Pharmacology 9th Edition Chapter 6 Choline Receptor Agonists

A mind map about choline receptor agonists, including M choline receptor agonists, N choline receptor agonists, etc. Hope this helps!

Edited at 2023-11-25 16:15:47

PlotWizard

Recent works View more works>>

Pharmacology 9th Edition Chapter 6 Choline Receptor Agonists

PlotWizard

Recent works View more works>>

Recommended to you
Outline

Chapter 6 Choline Receptor Agonists

Overview: It can directly stimulate choline receptors and produce effects similar to acetylcholine.

Acetylcholine is an endogenous neurotransmitter in the central and peripheral nervous systems. Its main function is to stimulate muscarinic choline receptors (M choline receptors) and nicotinic choline receptors (N choline receptors). . The former is mainly distributed in effector cells innervated by parasympathetic postganglionic fibers, while the latter is mainly distributed in neuromuscular junctions (Nm receptors) and autonomic ganglia (Nn receptors).

Section 1 M choline receptor agonists

Overview: Divided into choline esters and naturally occurring cholinomimetic alkaloids. Most of the former have excitatory effects on both M and N, but mainly M choline receptors; the latter mainly excites M choline receptors

1. Choline esters

Acetylcholine (ACh)

Overview: It is a cholinergic neurotransmitter with unstable properties and is easily hydrolyzed by acetylcholinesterase in the body. Can exist in parasympathetic and sympathetic

Pharmacological effects

1. Cardiovascular system (slow, slow)

(1) Vasodilation: A small dose of ACh can relax blood vessels throughout the body, such as pulmonary blood vessels and coronary blood vessels. Its mechanism: stimulating the M3 choline receptor subtype of vascular endothelial cells, resulting in endothelium-dependent relaxing factor (NO, nitric oxide), thereby causing relaxation of adjacent smooth muscle cells. If the vascular endothelium is damaged, the above effects no longer exist, and instead can cause vasoconstriction. (Link to pathophysiology discussion)

(2) Weaken myocardial contractility (negative inotropic effect): ACh has no obvious effect on ventricular muscle. Mainly produced indirectly by affecting noradrenergic nerve activity.

(3) Slow down the heart rate: delay automatic depolarization

(4) Slow down the atrioventricular node and Purkinje fiber conduction (negative conduction effect): prolong the refractory period

(5) Shorten the atrial refractory period

2. Gastrointestinal tract: promote digestion

3. Urinary tract: promote urination

2. Alkaloids

Overview: There are mainly three natural alkaloids, such as pilocarpine, arecoline and muscarine.

(1) Pilocarpine (pilocarpine)

Pharmacological effects: Directly acts on the M choline receptors of effector organs innervated by postganglionic fibers of parasympathetic nerves (including sympathetic nerves that control sweat glands), and has obvious effects on the eyes and glands.

1. Eyes: miosis, lowering intraocular pressure, regulating spasm

(1) Miosis: Pilocarpine can stimulate the M choline receptor of the pupillary sphincter.

(2) Reduce intraocular pressure: Pilocarpine pulls the iris toward the center through miosis, thins the root of the iris, expands the anterior chamber angle gap around the iris, and promotes the discharge of aqueous humor (recall picture P54)

(3) Regulate spasm

The lens is elastic and tends to be slightly spherical. However, due to the pull of the suspensory ligament, it maintains a relatively flat state. The suspensory ligament is in turn controlled by the ciliary muscle, which is composed of two types of smooth muscles, circular and radial, with the circular muscle (innervated by the oculomotor nerve) being the main one. When the oculomotor nerve is excited or after the action of pilocarpine, the circular muscle contracts toward the center of the pupil, causing the suspensory ligament to relax, the lens diopter to increase, and near objects to be seen.

2. Glands

Larger doses of pilocarpine can significantly increase the secretion of sweat glands and salivary glands

Clinical application

1. Glaucoma: Mainly characterized by characteristic optic atrophy and visual field defect, accompanied by symptoms of increased intraocular pressure Pilocarpine can treat angle-closure glaucoma (congestive glaucoma). Its pathogenic mechanism is poor circulation of aqueous humor.

2. Iridocyclitis: Use alternately with mydriasis (such as atropine) to prevent adhesion between the iris and the lens.

(2) Muscarine

Section 2 N-choline receptor agonists

Nicotine (nicotine): Its effect on ganglion Nn choline receptors is biphasic, with brief excitation at the beginning and then continuous inhibition; its effect on neuromuscular junction Nm receptors is similar, and its blocking effect can quickly mask its excitement. Causes muscle paralysis. Only toxicological effects